Peridot in Basalt (Olivine)
Olivine var. Peridot (Forsterite-Fayalite series) · Mineral Specimen / Semi-Precious Gemstone (when faceted).
Crystal System
Orthorhombic; typically occurs as granular aggregates or rounded grains within volcanic matrix.
Mineral Group
Silicates (Nesosilicates); Olivine group.
Chemical Formula
(Mg, Fe)2SiO4 (Magnesium Iron Silicate)
Formation Process
Igneous formation; crystallizes at very high temperatures deep within the earth's mantle and is carried to the surface in basaltic magmas/xenoliths during volcanic eruptions.
About This Crystal
The specimen features vibrant, lime-green to olive-yellow crystalline grains embedded within a dark, porous, vesicular basaltic matrix. The luster is vitreous (glassy) and the crystals appear translucent to transparent with a granular surface texture.
Physical Characteristics
Color: Olive-green; Streak: Colorless/White; Cleavage: Poor (1 plane); Fracture: Conchoidal to brittle; Specific Gravity: 3.27–3.37; Luster: Vitreous; Non-magnetic; Non-fluorescent.
Optical Properties
Refractive Index: 1.654–1.690; Birefringence: 0.035–0.038 (High); Doubly refractive; Strong pleochroism in large crystals; No significant fire or dispersion in matrix form.
Hardness & Durability
Origin Region
Notable sources include San Carlos Apache Reservation (Arizona, USA), Lanzarote (Canary Islands), and Peridot Mesa. Found in mafic volcanic rocks like basalt.
Hardness & Durability
Mohs Hardness: 6.5–7.0; Toughness: Fair to good; Sensitive to thermal shock (rapid temperature changes) and acids.
Care & Maintenance
Wash with warm soapy water and a soft brush; avoid ultrasonic or steam cleaners as they may crack the basalt or the crystal. Store away from harder gems like sapphires or diamonds to prevent scratching.
Rarity & Value
Common as a mineral specimen in volcanic regions, but gem-quality clean crystals are uncommon. Value is modest for matrix specimens, increasing with color saturation and transparency.
Special Characteristics
Vesicular basalt matrix (gas bubbles); high magnesium content (forsterite) gives it the distinctive green color without requiring trace elements like chromium.
Lore & History
Known as the "Gem of the Sun" by ancient Egyptians who mined it on the island of Zabargad. Traditionally associated with the Heart Chakra, it is believed by some to bring abundance and protection, though these are cultural rather than scientific claims.